Schematic Diagram: a diagram that depicts the construction of an electrical apparatus/circuit, containing standardized symbols representing parts of the electrical circuit including wires, bulbs, batteries, switches, etc.
Schematic Diagrams are necessary to understand the construction/arrangement of the parts of the circuit.
Understanding these components and the effect of certain arrangements in a circuit can show how current and potential difference can be altered and effected in portions of the circuit.
Schematic Diagram Symbols can be seen below:
Electric Circuit: a set of electrical components connected so that they provide one or more complete paths for the movement of charges.
When a wire connects a the terminals of a batter to a light bulb, charges built up on one terminal of the battery have a path to follow to reach the opposite charges on the other terminal. They move in a uniform direction, causing a current, which heats the filament (resistor) of the bulb, causing it to glow.
Load: elements in a circuit that dissipate energy, such as bulbs.
Circuits consist of both a load and a source of potential difference and electrical energy, such as a battery.
Closed circuit: a circuit that has a closed loop path from one terminal to the other. This entails having a switch, which, when closed, completes the circuit and allows the electrons to pass from the positive terminal to the negative terminal.
Open circuit: there is not a complete path for the electrons to follow, so there is no current and the circuit is unsuccessful.
Emf: the energy per unit charge supplied by a source of electric current. It is the source of potential difference and electrical energy in the circuit. Examples are batteries and generators.
The terminal voltage, or the potential difference across the terminals, is slightly less than the emf.
The potential difference across a load is the same as the terminal voltage.
20-2: Resistors in Series or in Parallel
Series: A circuit or a part of a circuit that has a single conducting path without junctions.
Resistors in a series have the same current. This is due to the conservations of charge: charges cannot build up or disappear at a point. The amount of charge that enters a bulb equals the amount of charge that leaves the bulb and continues on through the circuit. In the case of a series, there is only one path for the charge to follow, and so the amount of charge remains the same throughout the circuit.
Current: amount of charge moving past a point per unit of time. Because the amount of charge is the same from bulb to bulb, the current similarly stays constant from bulb to bulb. The total current depends on how many resistors there are in the circuit, which add up to the equivalent resistance.
The potential difference is equal to the current multiplied by the resistance:
The equivalent resistance in a series is the sum of all the resistances in the circuit:
The current is the same throughout a series, so the potential difference is equal to the single current by the equivalent resistance.
It is vital that all of the components of a series circuit conduct because there is only one path through which the electrons can pass through. If one link is missing, the chain is broken and the circuit cannot be completed.
Parallel: two or more components in a circuit that are connected across common points or juncctions, proving seaparate conducting paths for the current.
Not all of the resistors in a parallel circuit have the same current. Some are on different paths, as opposed to the single path of the series circuit, and so the current varies from resistor to resistor, or path to path.
Resistors in a parallel circuit do have the same potential differences. Each consecutive resistor is connected to a similar point as their neighbor, and so the potential difference remains the same.
The sum of the currents equals the total current in a parallel circuit:
The equivalent resistance, through its relationship with the constant potential difference in parallel circuit, can be found by a reciprocal relationship with all of the resistors:
Because of the reciprocal relationship, the equivalent reistance must always be less than the smallest resistance in the circuit.
It is not necessary that all components of a parallel circuit conduct the current because there are more than one path in the circuit for the current to pass through. If one path is stunted by a nonconducting element, the current continues to pass through the functioning paths.
20-3: Complex Resistor Combinations
To find the equivalent resistance of a complex circuit, you must split portions of the circuit into parallel and series circuits. In the above system, you could combine the two parallel resistors, R2 and R3 to form a single resistor that would fit in the single path of a series circuit along with R1. In other cases, you might have to add two series resistors on a parallel circuit so that there is one resistor per parallel rung in the circuit. Depending on the complexity of the circuit, steps like the ones just mentioned might be necessary to perform multiple times before coming to a final equivalent resistance and then moving on to find the potential difference and current. Finding these results will also depend on the form of the circuit that the complex circuit is reduced to: series or parallel.
Chapter 20: Circuits and Circuit Elements
20-1: Schematic Diagrams and Circuits
Schematic Diagram: a diagram that depicts the construction of an electrical apparatus/circuit, containing standardized symbols representing parts of the electrical circuit including wires, bulbs, batteries, switches, etc.- Schematic Diagrams are necessary to understand the construction/arrangement of the parts of the circuit.
- Understanding these components and the effect of certain arrangements in a circuit can show how current and potential difference can be altered and effected in portions of the circuit.
Schematic Diagram Symbols can be seen below:Electric Circuit: a set of electrical components connected so that they provide one or more complete paths for the movement of charges.
- When a wire connects a the terminals of a batter to a light bulb, charges built up on one terminal of the battery have a path to follow to reach the opposite charges on the other terminal. They move in a uniform direction, causing a current, which heats the filament (resistor) of the bulb, causing it to glow.
- Load: elements in a circuit that dissipate energy, such as bulbs.
- Circuits consist of both a load and a source of potential difference and electrical energy, such as a battery.
- Closed circuit: a circuit that has a closed loop path from one terminal to the other. This entails having a switch, which, when closed, completes the circuit and allows the electrons to pass from the positive terminal to the negative terminal.
- Open circuit: there is not a complete path for the electrons to follow, so there is no current and the circuit is unsuccessful.
Emf: the energy per unit charge supplied by a source of electric current. It is the source of potential difference and electrical energy in the circuit. Examples are batteries and generators.20-2: Resistors in Series or in Parallel
Series: A circuit or a part of a circuit that has a single conducting path without junctions.The potential difference is equal to the current multiplied by the resistance:
The equivalent resistance in a series is the sum of all the resistances in the circuit:
The current is the same throughout a series, so the potential difference is equal to the single current by the equivalent resistance.
It is vital that all of the components of a series circuit conduct because there is only one path through which the electrons can pass through. If one link is missing, the chain is broken and the circuit cannot be completed.
Parallel: two or more components in a circuit that are connected across common points or juncctions, proving seaparate conducting paths for the current.
Because of the reciprocal relationship, the equivalent reistance must always be less than the smallest resistance in the circuit.
It is not necessary that all components of a parallel circuit conduct the current because there are more than one path in the circuit for the current to pass through. If one path is stunted by a nonconducting element, the current continues to pass through the functioning paths.
20-3: Complex Resistor Combinations
To find the equivalent resistance of a complex circuit, you must split portions of the circuit into parallel and series circuits. In the above system, you could combine the two parallel resistors, R2 and R3 to form a single resistor that would fit in the single path of a series circuit along with R1. In other cases, you might have to add two series resistors on a parallel circuit so that there is one resistor per parallel rung in the circuit. Depending on the complexity of the circuit, steps like the ones just mentioned might be necessary to perform multiple times before coming to a final equivalent resistance and then moving on to find the potential difference and current. Finding these results will also depend on the form of the circuit that the complex circuit is reduced to: series or parallel.
Pictures from:
http://my.hrw.com/tabnav/controller.jsp?isbn=0030724864 First Picture
http://www.ibiblio.org/kuphaldt/electricCircuits/DC/DC_5.html Second, Third, and Fourth Pictures